As per out previous post on WORLD AIDS DAY , this disease is transmitted by blood transfusion, unprotected vaginal or anal sex, using needles used by infected persons etc. So, by avoiding such acts we can easily prevent the disease.
When the virus enters the body, it starts to grow in numbers and affect CD4 lymphocytes. Thus it affects the immunity of a person. But the sign and symptoms of the disease does not come out at the same time. Rather it needs years (2-15 years) to show symptoms. When it enters the body, and infect someone some flu like symptoms may occur. Sometimes the person may be absolutely ok. But the person can definitely transmit the infection. When no symptoms occur and the disease cannot be diagnosed it is called window period. We are lucky to get a good immune system that fights off many bacterial, viral, fungal infection, some cancers etc. But as the disease AIDS, breaks the sound immunity, those diseases can affect easily. Diarrhoea, fever, oral thrush, Kaposi’s sarcoma, TB etc are the diseases that can easily affect the infected person. But any person whoever is suffering from a disease for long, it is not said the person has AIDS. That can be a chronic condition due to some other cause. That must be differentiated by proper diagnosis. Within 28 days of infection the disease can be diagnosed using serological tests. ELISA is a reliable method. Self testing methods are also available in some countries.
All those above-said informations are in a nut-shell about HIV-AIDS. I would like to refer the interested readers to the fact sheet published by WHO(World Health Organization). The link is given below: